devicetree: bindings: Extend the bma180 bindings with bma250 info

The bma180 / bma250 accelerometers share a driver (at least under Linux),
so it makes sense to also have their bindings info in a single .txt.

This commit extends the bma180 bindings with bma250 bindings, specifically
it specifies how the 2 seperate interrupts the bma250 has must be listed
in devicetree. The existing bma180 driver is already fully compatible
with the specified bindings.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rob Herring <robh@kernel.org>